Catalyst system for deodorization and apparatus for deodorization using the same

ABSTRACT

A catalyst system for deodorization and an apparatus for deodorization, each of which comprises a pretreating catalyst and a noble metal catalyst, the pretreating catalyst converting a sulfur atom of low oxidation state which deactivates the noble metal catalyst into a sulfur atom of high oxidation state which has little deactivation effects there on, the noble metal catalyst oxidizing aldehyde, etc., wherein a material to be deodorized is brought into contact with the pretreating catalyst prior to being brought into contact with the noble metal catalyst. As the pretreating catalyst, a catalyst comprising at least one selected from the group consisting of vanadium, chromium, manganese, iron, cobalt, nickel, copper and oxides thereof is used, while as the noble metal catalyst, a catalyst comprising at least one selected from the group consisting of ruthenium, rhodium, palladium, silver, rhenium, osmium, iridium, platinum and gold is used. According to the catalyst system, a striking deodorizing-effect is provided to, in particular, a mixture of sulfur compounds of low oxidation state and compounds such as aldehydes or alcohols.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a catalyst for deodorization anda deodorizing apparatus using the same catalyst is used and inparticular, relates to a catalyst for deodorization which provides anexcellent deoderization effect to a mixture of sulfur compounds andcompounds such as aldehydes, alcohols or hydrocarbon compounds, and anapparatus for deodorization using the same.

[0003] 2. Prior Art

[0004] Hitherto, noble metal catalysts in which platinum, palladium, orboth platinum and palladium are supported on a proper support have beenused as a catalyst for deodorization. These catalysts promote a reactionwherein a gas to be deodorized is oxidized and decomposed by oxygen inair so as to provide a deodorization effect, which are, in particular,effective on aldehydes, alcohols and hydrocarbon compounds.

[0005] However, These catalyst are deactivated by materials to bedeodorized which contain sulfur compounds of low oxidation state such asdimethyl sulfide or methanethiol. Therefore, when such materials to bedeodorized are contained, it is difficult to use these catalyst as thedeordorization catalyst.

[0006] In case of materials to be deodorized which contain sulfurcompounds, catalysts having an oxide of cobalt, manganese, etc. as anactive component, which have relatively strong resistance against suchmaterials are used. For example, Japanese Patent KOKAI(Laid-Open)No.31128/94 discloses a deodorant which comprises an oxide of cobaltand/or manganese, and zeolite. Furthermore, in Japanese Patent KOKAINos.47645/96 and 284670/95, a catalyst containing an activated manganesedioxide, a copper-supporting zeolite and copper oxide as an effectivecomponent is used so as to attempt a deodorization thereby. However, allof such catalysts provide some effects on the sulfur compounds, whileinsufficient or no effects on aldehydes, alcohols and the like.

[0007] On the other hand, gases, which are emitted from crude wastedisposal machines, contain aldehydes, amines, alcohols and the like aswell as we sulfur compounds, and therefore, it was impossible to treatsuch gases, with the conventional cataysts mentioned above.

SUMMARY OF THE INVENTION

[0008] It is, because a sulfur atom of dimethylsulfide or the likestrongly adsorbs on active sites of the noble metal catalysts mentionedabove, that these catalysts are deactivated by dimethylsulfide or thelike. It has been found that the effect that the catalyst is deactivatedby such an adsorption is remarkable in compounds which have a sulfuratom of low oxidation state, while such effect is little observed in asulfur compound of high oxidation state. The present inventor has beenfound that prolongation of life of the noble metal catalyst and ahigh-efficient oxidative decomposition are realized by using in acombination of the noble metal catalyst and a catalyst which oxidizescompounds having a sulfur atom of low oxidation state such asdimethylsulfide to a high oxidation state such as sulfons.

[0009] It is an object of the present invention to provide a catalystsystem which has an effective deodorization effect on materials to bedeordorized which contain a compound such as aldehydes, alcohols, aminesor hydrocarbon compounds, as well as sulfur compounds of low oxidationstate.

[0010] It is another object of the present invention to provide anapparatus in which a catalyst system is arranged so that the catalystsystem has an effective deodorization effect on materials to bedeordorized which contain compounds such as aldehydes, alcohols, aminesor of hydrocarbon compounds, as well as sulfur compounds of lowoxidation state.

[0011] According to one aspect of the present invention, there isprovided a catalyst system for deordorization, which comprises apretreating catalyst and a noble metal catalyst, the pretreatingcatalyst being a catalyst for converting a sulfur compound of lowoxidation state which is included in materials to be deordorized into asulfur compound of high oxidation state, wherein the materials to bedeordorized are brought into contact with the pretreating catalyst priorto being brought into contact with the noble metal catalyst.

[0012] According to another aspect of the present invention, there isprovided an apparatus for deordorization which is provided with acatalyst tower inside which the pretreating catalyst is positionedupstream of channels for a gas to be deodorized, and the noble metalcatalyst is positioned downstream of the channels, wherein thepretreating catalyst is the one for converting the sulfur compound oflow oxidation state which is included in the gas to be deodorized intothe sulfur compound of high oxidation state.

[0013] Furthermore, the catalyst system for drozination of the presentinvention is characterized by comprising the pretreating catalyst andthe noble metal catalyst, the pretreating catalyst comprising at leastone selected from the group consisting of vanadium, chromium, manganese,iron, cobalt, nickel, copper and oxides thereof, and the noble metalcatalyst comprising at least one selected from the group consisting ofruthenium, rhodium, palladium, silver, rhenium, osmium, iridium,platinum and gold.

[0014] In particular, the catalyst system for deordorization of thepresent invention preferably comprises the pretreating catalyst whichcontains manganese oxide(IV) and/or vanadium oxide(V), and the noblemetal catalyst which contains palladium and/or platinum.

[0015] Further another aspect of the present invention relates to a useof the catalyst system which comprises the noble metal catalyst and thepretreating catalyst for deodorizing a malodorous gas containingmaterials which provides a deactivation effect on the noble metalcatalyst, wherein the use comprises the steps of: bringing the gas to bedeodorized which contains materials which provides the deactivationeffect on the noble metal catalyst into contact with the pretreatingcatalyst prior to bringing the gas into contact with the noble metalcatalyst so as to convert the gas into other materials having lessdeactivation effect; and then, bringing the gas into contact with thenoble metal catalyst.

BRIEF EXPLANATION OF THE DRAWINGS

[0016]FIG. 1 is an explanation drawing which illustrates an example ofthe apparatus for deodorization of the present invention; and

[0017]FIG. 2 is an explanation drawing which illustrates another exampleof the apparatus for deodorization of the present invention.

PREFFERED MODES OF EMBODIMENT

[0018] As the pretreating catalyst in the present invention, a catalystwhich comprises at least one selected from the group consisting ofvanadium, chromium, manganese, iron, cobalt, nickel, copper, and oxidesthereof is suitably used. The pretreating catalyst is constituted by anoxidation catalyst which has relatively strong resistance againstcompounds having a sulfur atom of low oxidation state, which takes apart to oxidize compounds containing a sulfur atom of low oxidationstate such as disulfides to materials of high oxidation state such assulfones. At this time, it is necessary to control the oxidation powerthereof so that the compound can be requisitely and sufficientlyoxidized to sulfone. According to the catalyst for deodorization of thepresent invention, the metals and their oxides which are included in theabove group can be suitably selected or combined together depending uponthe composition of a gas to be deodorized so as to control the oxidationpower thereof. It is effective to use manganese oxide(IV) and/orvanadium oxide(V), in particular, when the pretreating catalystcomprising manganese oxide(IV) and 5 to 20% by weight of vanadiumoxide(V) (the whole catalyst is represented as 100% by weight) is used,a catalyst which is effective on many gases to be deodorized can berealized. A manganese oxide(IV)-vanadium oxide(V) can be preparedaccording to various methods, for example, as follows. Namely, manganeseoxide(IV) which is obtained by decomposing potassium permanganate withnitric acid and vanadium oxide(V) which is obtained by decomposingammonium metavanadate at a temperature of 500° C. in an air flow aremixed in desired amounts, and said mixture is fired at a temperature of200° C. in an oxygen flow so as to obtain a manganese oxide(IV)-vanadiumoxide(V) of the present invention. Incidentally, a support is notnecessary for this catalyst except special occasions. Furthermore,depending upon the use of the catalyst, the form of an apparatus, theflow rate of a gas to be deodorized or the like, the shape of thecatalyst may be suitably selected from tablets, fine particles,honeycombs and the like.

[0019] The noble metal catalyst takes a part to oxidize aldehydes,alcohols, amines and hydrocarbon compounds, which is preferably selectedfrom the group consisting of ruthenium, rhodium, palladium, silver,rhenium, osmium, iridium, platinum and gold. Then the compound havingsulfur atom of low oxidation state which causes the deactivation of thenoble metal catalyst is oxidized by the pretreating catalyst so as to beconverted into compounds having sulfur atom of high oxidation state suchas sulfones which have little deactivation effects. Therefore theprolongation of life of the noble metal catalyst and a high-efficientoxidative decomposition can be realized. The noble metal catalyst can besuitably selected from metals which are contained in the group mentionedabove, or can be obtained by a combination of said metals so as toincrease deordorization efficiency. In particular, it has been confirmedthat a catalyst which is effective to many different kinds of gases tobe deodorized is realized by using platinum or gold. Furthermore,although a support for the noble metal catalyst is not particularlylimited, for example, γ-alumina or the like can be used.

[0020] Thus, as a catalyst system for deororization is in combination ofthe pretreating catalyst to oxidize compounds containing sulfur atom oflow oxidation state into sulfones, and the noble metal catalyst tooxidize aldehydes into carbon dioxide and water, the prolongation oflife of the noble metal catalyst and a high-efficient oxidativedecomposition can be realized, wherein as the use mode of the catalystfor deordorization of the present invention, the pretreating catalyst isdesirably positioned upstream of channels for a gas to be deodorized,and the noble metal catalyst is desirably positioned downstream of thechannels, because the compound including sulfur atom of low oxidationstate can be effectively converted into sulfones by such an arrangement.

[0021] The catalyst system for deordorization of the present inventionis effective on aldehydes, alcohols, amines, and hydrocarbon compounds,and furthermore effective on compounds which contain a sulfur atom oflow oxidation state such as sulfides, disulfides or alkylthiols. Inparticular, the catalyst is effective on a mixture of the aldehydecompound and the sulfur compound.

[0022] The apparatus for deodorization of the present invention ischaracterized in that the pretreating catalyst and the pecious metalcatalyst as mentioned above are arranged in series inside a catalyticreaction tower, wherein the pretreating catalyst is positioned upsteamof channels for a gas to be deodorized, while the pecious metal catalystis positioned downsteam of the channels. If such conditions aresatisfied, the form of a general catalytic reaction tower which has beenused hitherto can be used as it is. As shown in FIG. 1, pretreatingcatalyst bed (5) is positioned upstream of gas to be deodorized (2) asshown by arrows, while noble metal catalyst bed (6) is positioneddownstream thereof, wherein the catalyst beds (5) and (6) are properlyspaced, provided that both catalysts are not mixed with each other, anda space between the catalyst beds (5) and (6) is not specificallylimited. Heater (3) is positioned in the jacket of reaction tower (1).After treatment, deodorized gas (4) is removed.

[0023] Furthermore, as shown in FIG. 2, the pretreating catalyst bed (5)and the noble metal catalyst bed (6) can be arranged by bringing bothcatalyst beds (5) and (6) into contact with each other not to be mixedwith each other. When a pellet-shaped catalyst is used, the boundary ofboth catalyst beds is preferably comparted by, for example, a wirenetting. On the other hand, when at least one of both catalysts is amonolithic catalyst, for example, a catalyst which was formed in theshape of a honeycomb, the compartment therebetween is unnecessarybecause there is no possibility of both catalysts to be mixed with eachother. Incidentally, the shape of the catalyst tower (1) does notspecifically matter. Such a structure of the catalytic reaction towercan provide effective treatment on compounds including sulfur of lowoxidation state which deactivate the noble metal catalyst, andfurthermore can achieve the high efficiency of the catalyst and theprolongation of the life thereof.

[0024] Conditions for deodorizing the gas by using the catalyst fordeodorization of the present invention are suitably selected accordingto the kind of the gas to be deodorized; for example, preferably thereaction temperature is in the range of 200° C. to 400° C. , and thespace velocity (SV) is in the range of about 1000 to 10000 h⁻¹.Furthermore, a contact system for bringing the gas to be deodorized intocontact with the catalyst is preferably a fixed bed, while the contactsystem in which a fluidized bed or a moving bed is employed can be alsoused under such conditions that the pretreating catalyst and the noblemetal catalyst are not mixed with each other.

EXAMPLES

[0025] Hereinafter, the present invention will be more specificallyexplained by the following examples.

Example 1

[0026] A catalyst system for deodorization of the present inventionwhich comprises a pretreating catalyst and a noble metal catalyst wasused, wherein the pretreating catalyst comprises manganese oxide(IV) andvanadium oxide(V) in an amount of 5% by weight (in which all of saidcatalysts was represented as 100% by weight), and the noble metalcatalyst comprises a platinum-supporting alumina catalyst in which 1% ofplatinum is supported; and an apparatus for deodorization of the presentinvention is shown in FIG. 1, wherein a silica tube(having an innerdiameter of 16 mm and a length of 500 mm) as catalyst tower (1),pretreating catalyst bed (5) and noble metal catalyst bed (6) areprovided, wherein the silica tube was filled with the pretreatingcatalyst bed (5) having a volume of 10 cm³ and the noble metal catalystbed (6) having a volume of 5 cm³, the pretreating catalyst bed (5) andthe noble metal catalyst bed (6) being spaced about 2 cm apart; andthereby a simulated malodorous air including 10 ppm of dimethylsulfideand ethanal(acetaldehyde) having the same concentration was treated at atemperature of 3000 C under the condition of Sv/h⁻¹30000. 96% ofDimethylsulfide and 100% of ethanal were oxidized and removed,respectively. Although the treatment was carried on for a period of 100hours, no deterioration in activation was observed.

Comparative Example 1

[0027] A treatment was carried out under the same conditions as that inExample 1 except that only the platinum-supporting alumina catalyst inwhich 1% of platinum is supported was used instead of the atalyst systemfor deodorization of the present invention. In the early stage ofreaction, the removal ratio of dimethylsulf ide was 34%, while that ofethanal was 63%. According to measurements after the simulatedmalodorous air was passed through for a period of 100 hours, the removalratio of dimethylsulfide was 2%, while that of ethanal was 9%.

Example 2

[0028] The same apparatus for deodorization as that used in Example 1was filled with a catalyst system for deodorization of the presentinvention which comprises a pretreating catalyst and a noble metalcatalyst, wherein the pretreating catalyst comprises manganese oxide(IV)and vanadium oxide(V ) in an amount of 20% by weight, the noble metalcatalyst compris a platinum-palladium supporting alumina catalyst inwhich platinum and palladium were supported by 1.5%, respectively; andthen a simulated malodorous air which includes 100 ppm ofmethanal(formaldehyde), trimethylamine in an amount of the sameconcentration, and 10 ppm of methanethiol was treated at a temperatureof 300° C. under the condition of SV/h⁻¹=30000. 99% of Methanal, 94% oftrimethylamine and 97% of Methanethiol were oxidized and removed.Although the treatment was carried on for a period of 100 hours, nodeterioration in activation was observed.

Example 3

[0029] The same apparatus for deodorization as that in Example 1 wasfilled with a catalyst system for deodorization of the present inventionwhich comprises a pretreating catalyst and a noble metal catalyst,wherein the pretreating catalyst comprises manganese oxide(IV) andvanadium oxide(V) in an amount of 5% by weight, the noble metal catalystcomprises a palladium-supporting alumina catalyst in which 1.5% ofpalladium was supported; and then a simulated malodorous air whichincludes 330 ppm of acetic acid and 480 ppm of ethanal was treated at atemperature of 380° C. under the condition of SV/h⁻¹=10000. Both aceticacid and ethanal were removed by 100%, respectively.

Comparative Example 2

[0030] When a treatment was carried out under the same conditions asthat in Example 3 except that only manganese oxide(IV) containing 5% byweight of vanadium oxide(V) was used instead of the catalyst system ofthe present invention, the removal ratio of acetic acid was 61%, whilethat of ethanal was 48%. Furthermore, when the treatment was carried outunder the same conditions as that in Example 3 except that only apalladium-supporting alumina catalyst in which 1.5% of palladium wassupported was used instead of the catalyst system of the presentinvention, the removal ratio of acetic acid was 68% while that ofethanal was 78%. From these results, assuming that there is nosynergistic effect of both catalysts, the removal ratio of acetic acidcomes to about 88%, while that of ethanal comes to about 89%. On theother hand, since according to the catalyst system of the presentinvention, the removal ratios of acetic acid and ethanal are 100%,respectively, it is clear that a catalyst system of the presentinvention provides more excellent effects as compared with a merecombination of the effect of each individual catalyst, which shows thata material which provides a deactivation effect to the noble metalcatalyst is converted into another material, thereby the deodorizationefficiency of the noble metal catalyst is strikingly improved.

Example 4

[0031] The same apparatus for deodorization as that in Example 1 wasfilled with the catalyst system for deodorization of the presentinvention which comprises the pretreating catalyst and the noble metalcatalyst, wherein the pretreating catalyst comprises manganeseoxide(IV), 1% by weight of nickel oxide(II), and 5% by weight ofvanadium oxide(V), the noble metal catalyst comprises aplatinum-ruthenium supporting alumina catalyst in which platinum andruthenium were supported by 2%, respectively; and then a simulatedmalodorous air which includes 100 ppm of dimethylsulfide, 100 ppm ofmethanethiol, 100 ppm of limonene and 100 ppm of ethanal was treated ata temperature of 400° C. under the condition of SV/h⁻¹=10000. 98% ofDimethylsulfide, 93% of methanethiol, 99% of limonene and 99% of ethanalwere treated, respectively. Although this treatment was carried on for aperiod of 100 hours, no deterioration in activation was observed.

Example 5

[0032] The same simulated malodorous air as that in Example 4 wastreated under the same conditions as those in Example 4 except that thecatalyst system for deodorization of the present invention whichcomprises a pretreating catalyst and a noble metal catalyst was used,wherein the pretreating catalyst comprises manganese oxide(IV), 1% byweight of nickel oxide(II), and 10% by weight of vanadium oxide(V), thenoble metal catalyst comprises a rhodium-palladium supporting aluminacatalyst in which rhodium and palladium were supported by 1% by weight,respectively. 95% of Dimethylsulfide, 96% of methanethiol, 100% oflimonene and 96% of ethanal were treated, respectively. Although thistreatment was carried on for a period of 100 hours, no deterioration inactivation was observed.

Example 6

[0033] The same simulated malodorous air as that in Example 5 wastreated under the same conditions as those in Example 5 except thatmanganese oxide(IV) and 5% by weight of vanadium oxide(V) are used asthe pretreating catalyst. 96% of Dimethylsulfide, 97% of methanethiol,98% of limonene and 97% of ethanal were treated, respectively. Althoughthis treatment was carried on for a period of 100 hours, nodeterioration in activation was observed.

[0034] As mentioned above, the catalyst system for deodorization of thepresent invention can effectively decompose and/or deodorize a gas to bedeodorized which includes aldehydes, sulfur compounds of low oxidationstate, or other compounds. Furthermore, it is also possible topreponderantly remove a material to be removed with top priority bysuitably selecting the kind of a catalyst.

[0035] Effects of the Invention:

[0036] As mentioned above, according to the present invention, thepretreating catalyst and the noble metal catalyst are used, and a gas tobe deodorized is brought into contact with the pretreating catalystpriot to being brought into contact with the noble metal catalyst,wherein the pretreating catalyst can convert a sulfur atom of lowoxidation state by which the noble metal catalyst is deactivated, into asulfur atom the high oxidation state which has little deactivationeffects, and the noble metal catalyst can oxidize aldehydes; and therebythe catalyst system for deodorization which shows a high deodorizationon to a mixture of compounds such as aldehydes and sulfur compounds, andhas high resistance against the same, is provided.

[0037] On the other hand, in the apparatus for deodorization of thepresent invention, the pretreating catalyst is positioned upstream ofthe channels of a gas to be deodorized, while the noble metal catalystis positioned downstream thereof, and therefore, compounds containing asulfur atom of low oxidation state have been effectively converted intosulfur compounds of high oxidation state such as sulfone through thepretreating catalyst, and thereafter the deodorization treatment iscarried out through the noble metal catalyst, and thereby theprolongation of life of the noble metal catalyst and a high-efficientoxidative decomposition can be realized.

What is claimed is:
 1. A catalyst system for deodorization, comprising apretreating catalyst for converting sulfur compounds of low oxidationstate which are contained in materials to be deodorized, into sulfurcompounds of high oxidation state and a noble metal catalyst, whereinsaid material to be deodorized is brought into contact with saidpretreating catalyst prior to being brought into contact with said noblemetal catalyst.
 2. The catalyst system for deodorization according toclaim 1 , wherein said pretreating catalyst is a catalyst comprising atleast one selected from the group consisting of vanadium, chromium,manganese, iron, cobalt, nickel, copper and oxides thereof, while saidnoble metal catalyst is a catalyst comprising at least one selected fromthe group consisting of ruthenium, rhodium, palladium, silver, rhenium,osmium, iridium, platinum and gold.
 3. An apparatus for deodorizationwhich is provided with a catalytic reaction tower inside which channelsfor a gas to be deodorized are provided, wherein a pretreating catalystbed for converting sulfur compounds of low oxidation state which arecontained in said gas into sulfur compounds of high oxidation state ispositioned upstream of said channels for said gas, while a noble metalbed is positioned downstream of said channels.
 4. The apparatus fordeodorization according to claim 3 , wherein said pretreating catalystis a catalyst comprising at least one selected from the group consistingof vanadium, chromium, manganese, iron, cobalt, nickel, copper andoxides thereof, while said noble metal catalyst is a catalyst comprisingat least one selected from the group consisting of ruthenium, rhodium,palladium, silver, rhenium, osmium, iridium, platinum and gold.
 5. Theapparatus for deodorization according to claim 3 , wherein inside thecatalytic reaction tower, said pretreating catalyst bed is upstreampositioned, and said noble metal catalyst bed is downstream positioned,wherein said pretreating catalyst bed and said noble metal catalyst bedare positioned in series at desired space.
 6. The apparatus fordeodorization according to claim 3 , wherein inside the catalyticreaction column, said pretreating catalyst bed is upstream positioned,and said noble metal catalyst bed is downstream positioned, wherein saidpretreating catalyst bed and said noble metal catalyst bed are not mixedwith each other, and are kept in contact with each other.
 7. A use of acatalytic system comprising a pretreating catalyst and a noble metalcatalyst for deodorizing a gas which contains materials having adeactivation effect on the noble metal catalyst, wherein said usecomprises the steps of: bringing said gas to be deodorized into contactwith said pretreating catalyst prior to bringing said gas into contactwith said noble metal catalyst so as to convert said gas into anothermaterial having less deactivation effect; and then, bringing said gasinto contact with-said noble metal catalyst.
 8. The use of a catalyticsystem according to claim 7 , wherein said pretreating catalyst is acatalyst comprising at least one selected from the group consisting ofvanadium, chromium, manganese, iron, cobalt, nickel, copper and oxidesthereof; and said noble metal catalyst is a catalyst comprising at leastone selected from the group consisting of ruthenium, rhodium, palladium,silver, rhenium, osmium, iridium, platinum and gold.